Diamond fluorescence is one of the most confusing topics in the diamond industry, even for jewelers. This is unfortunate because if one were to spend a few minutes bifurcating the information on this topic they would simply find that diamond fluorescence is good for diamonds that are further down the color spectrum and bad for diamonds that approach the top end. Here’s the entire analysis in three minutes.
This depends on a few things. First, understand that florescence crosses over two of the four C’s – color and clarity. Diamond Fluorescence is positive for color and negative for clarity, but only under very specific light conditions.
When diamonds are exposed to ultraviolent radiation they emit a visible light called florescence. Ultraviolet radiation is invisible, but it is everywhere – particularly in sunlight. This means you won’t see the input (UV light), but you can see the output (florescence) if you are standing in the sun or other UV sources and the gemstone has meaningful fluorescence. You can see fluorescence in about one out of three diamonds (35%).
Strong blue fluorescence can make a light-yellow diamond look closer to colorless in sunlight. This is because blue and yellow are color opposites, and they cancel each other out. However, if the fluorescence is strong the diamond will look cloudy or oily and this will lower the value of the diamond.
Diamond fluorescence is good in moderation, but you should not buy a diamond with strong blue fluorescence. Further if you are buying a gem approaching colorless (D, E, F, G, H, I, J) there is absolutely no benefit to fluorescence in a diamond. The benefit is related to stones with a higher yellow content (K+) and only in very specific circumstances (in the sun, perfect lighting conditions, etc.).
Conversely diamond fluorescence probably won’t hurt anything either as long as it is not strong.
The optical value of moderate fluorescence is slightly higher in lower color grade diamonds and lower in higher in lower color grade diamonds, but on balance it does not mean much.
We hope this helps demystify diamond fluorescence for you.